The present invention generally relates to a semi-active anti-roll suspension system having a pair of independently mounted stabilizer bar halves, which may be coupled to one another to control vehicle roll and more particularly to an apparatus and method for controlling the coupling of the stabilizer bar halves.
Traditional vehicle suspension systems include resilient devices, such as coil springs and leaf springs, to flexibly support a portion of a vehicle and enable all of the wheels to maintain contract with the ground when traversing uneven terrain. Segregating the vehicle into unsprung and sprung portions in this manner is also useful for preventing severe impulsive forces from being transmitted to the vehicle occupants.
It is known that when vehicle travels around a corner, centrifugal forces acting on the vehicle tend to cause the sprung portion of the vehicle to roll. In severe instances, the effects of roll can cause instability and impede the ability of the driver to control the vehicle. Although the effects of roll are more pronounced with vehicles having a comparatively high center of gravity, such as vans or trucks, every vehicle is affected by roll.
In tuning the ride and handling of a vehicle, it is often desirable to soften or lower the spring rate of the suspension""s springs to provide a softer, less harsh ride. One of the main drawbacks associated with this approach is that a suspension system having springs with a relatively low spring rate permits the vehicle body to roll at a relatively higher rate. Accordingly, it would seem that the combination of springs with a very low spring rate and a relatively stiff stabilizer bar would optimize both the ride and handling of the vehicle.
The relatively stiff stabilizer bar, however, tends to directly connect the vehicle wheels such that the motion of one wheel is copied to another wheel. If a vehicle so equipped was to strike a bump with one wheel, for example, the upward force (i.e., jounce) imparted to that wheel would be transmitted through the stabilizer bar to the opposite wheel, causing the opposite wheel to move in an upward direction. This xe2x80x9ccross-talkxe2x80x9d between the vehicle wheels is highly undesirable as it adversely affects vehicle ride.
Another drawback of stabilizer bars is that their torsional stiffness inhibits the free travel of the vehicle wheels. Modern materials and design techniques have substantially reduced the weight of the vehicle wheels and mounting structures to such an extent that the weight of a wheel and its mounting structure is typically insufficient to cause the stabilizer bar to rotate. While this problem is rarely, if ever, noticed on the relatively flat surfaces of modern roads, it can become apparent when the vehicle is operated over un-even terrain. In some situations, it is possible for one of the vehicle wheels to remain in an elevated position over a dip in the terrain due to the torsional resistance of the stabilizer bar. While situations of this severity are not routinely encountered, the fact remains that the stabilizer bar reduces vehicle traction in some situations.
One solution to the above-mentioned drawbacks is disclosed in copending and commonly assigned U.S. patent application Ser. No. 09/663,613 entitled xe2x80x9cSemi-Active Anti-Roll Systemxe2x80x9d, the disclosure of which is hereby incorporated by reference as if fully set forth herein. This system employs a pair of stabilizer bar members, which are selectively uncoupled via a clutch assembly to improve vehicle traction in some situations. Despite the numerous advantages of this system, it is susceptible to improvement.
For example, it is highly desirable to provide a clutch controller for causing the stabilizer bar members to couple in response to a fault in the transmission of electrical power to the clutch assembly. Configuration in this manner may compromise vehicle traction in some situations, but effectively ensures that the vehicle will not be operated at high rates of speed with the stabilizer bar members disconnected.
In another example wherein a pair of these stabilizer bar systems are incorporated into a vehicle for the front and rear axles of the vehicle, it is highly desirable to control the coupling and disconnecting of the stabilizer bar members so as to improve vehicle stability and eliminate any roll-over steering effect that is generated as a result of the method by which the stabilizer members are connected and disconnected.
In one preferred form, the present invention provides a reserve powering apparatus for powering a clutch assembly in the event of an electrical failure, which prevents the vehicle power source from transmitting electrical power to the clutch assembly.
In another preferred form, the present invention provides a speed sensing apparatus for inhibiting the operation of the stabilizer bar assembly in a disengaged condition if the speed of the vehicle is greater than or equal to a predetermined speed threshold.
In yet another preferred form, the present invention provides a methodology for controlling the engagement and disengagement of a pair of stabilizer bar assemblies.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.